Apparatus for the heat treatment of metallic sheet material



April 21, 1959 2,883,172-

APPARATUS FOR THE HEAT TREATMENT OF METALLIC SHEET MATERIAL Filed Aug.4, 1955 R. N. MI TCHELL 2 Sheets-Sheet 1 INVENTOR.

RANDOLPH N. MITCHELL ATToR NEYT April 21, 1959 R. N. MITCHELL I2,333,172

APPARATUS FOR Tl-E HEAT TREATMENT OF METALLIC SHEET MATERIAL Filed Au4,1955 2 Sheets-Sheet '2 53 SHRINKAGE I I I 54 I 54:- LENGTHWISE 52ALUMINUM I SHEET I j snLisHzs E ALUMINUM g SHEET SHRINKAGE ALUMINUM Fig-SHEET 3 WIDTHWISE 1LBRUSHES INVENTOR.

RANDOLPH. N. MITCHELL ATTORNEY nited Sttes Pater i."

pen

APPARATUS FOR THE HEAT TREATMENT OF METALLIC SHEET MATERIAL Randolph N.Mitchell, La Grange, Ill., assignor to Reyholds Metals Company,Richmond, Va., a corporation of Delaware Application August 4, 1955,Serial No. 526,419

1 Claim. (Cl. 2636) The present invention relates to means for conveyingsheet material and especially to means for conveying sheet material thatis susceptible to marking or scratching.

More particularly the present invention has special utility in conveyinghot aluminum sheets through an annealing furnace. In the preparation ofsheet aluminum it is necessary to convey the sheets from point to pointfor the purpose of performing various operations on the individualsheets. One such operation is that of annealing. The sheets are conveyedto an annealing furnace which is customarily of considerable length. Theconveyor will then pass the sheets through the furnace where they aresuitably heated and then conveyed to a cooling chamber.

At the present time, the sheets are generally conveyed by cableconveyors. The conveyor is made of a number of strands of smallstainless steel cable upon which the individual sheets are supported. Asthe sheets are thus transported, the relative movement between thecables and the sheets causes scratching or marking of the undersurfaceof the sheets. This scratching is primarily due to the relative movementof the sheet and conveyor. This relative movement is always present asthe sheet passes through the annealing furnace because of the expansionand contraction of the material. This marking or scratching is furtheraggravated during the annealing process because the sheets are in ahighly heated condition and in a softer state than they are at roomtemperature. This marking is present in greater or lesser degree in allcable conveyor annealed aluminum and has come to be known to the tradeas cable marks.

This scratching of the sheet material is not limited to cable conveyors.When other conveyors such as conventional walking beam or roller hearthtypes are used, the same problem of abrasion exists. One primary causeof the abrading or scratching is a result of foreign deposits or pickupon the conveyor structure. The relative motion and pressure between thealuminum sheets and the supporting conveyor structure causes aluminumand aluminum oxide to adhere to the supporting surfaces. This isespecially true at the high temperatures encountered in the annealingfurnace. As these deposits which have come to be known as pickupcontinue to build up, they abrade and scratch subsequent sheets withincreasing severity. In spite of the fact that the speeds of the sheetand supporting conveying means are carefully synchronized, the relativemotion therebetween resulting from thermal expansion and contraction ofthe sheets is suflicient to cause pickup. Of course, if there isrelative movement between the conveyor and sheet material due to othercauses such as shaking, vibratingor slipping, this too will result inscratching or abrading of the product. Fundamentally, therefore, it isseen that the cause of the problem is the relative movement .of conveyorand sheet. It is to this general problem that the present invention isdirected.

It is therefore an object of the present invention to provide animproved conveying mechanism.

Another object of the present invention is to provide a conveyingmechanism wherein the conveyed material will not be scratched, marked orabraded.

Another object of the present invention is to provide a conveyingmechanism wherein relative movement of the conveyed material andconveying or supporting media is substantially eliminated.

A more specific object of this invention is to provide a conveyingdevice especially adapted for conveying aluminum sheets through anannealing furnace.

In accordance with the above objects, the present invention contemplatesa conveyor having a somewhat flexible sheet supporting structure thatcontacts the conveyed material at a plurality of different points. Theflexible character of the supports permits lateral and transversemovement thereof as the point of contact of support and sheet isdisplaced due to expansion and contraction. In one embodiment of theinvention, wire brush surfaces are used to support the aluminum sheet.It should be noted that the pressure which any wire is capable ofexerting is limited by the column strength of the wire itself. Each wireis also capable of limited movement in that by bending or deflecting itcan follow its point of original contact with the sheet surface throughminor speed differentials and sidewise movement resulting fromexpansion, contraction or from mechanical irregularitim.

The invention will be more fully understood from the followingdescription of a specific embodiment thereof taken with the drawings inwhich:

Fig. l is a perspective view of a series of brush rolls and drivingmeans embodying the principles of the present invention and shown in adiagrammatically illustrated annealing furnace;

Fig. 2 is a perspective view of a modification of the conveyor of Fig.1;

Fig. 3 is a detailed cross-sectional view of a brush showing theposition of the bristles and the holding means therefor;

Fig. 4 is a perspective view of a further modification of the conveyorof Fig. 1;

Fig. 5 is a side elevation of a further modification of the above formsof the invention;

Figs. 6 and 7 illustrate the manner in which longitudinal and lateralexpansion of the sheets is compensated for by the flexibility of theconveyor support means; and

Figs. 8 and 9 illustrate the manner in. which longitudinal and lateralshrinkage or contraction of the sheets is compensated forby the conveyorsupport means.

Referring now to the drawings and more particularly to Fig. Lnumeral it}represents generally a conveying mechanism comprisinga series ofgenerally parallel rollers 11, 12 and 13. It is of course understoodthat a larger number of conveyor rollers may be used depending upon thedistance the material is to be conveyed, size of the material, etc. Forthe purposes of description it is suflicient to show three such rollers.These rollers may be suitably mounted within an annealing furnace orheat treating chamber 5 :having an inlet opening 6 for receiv ingaluminum sheets as it is for this operation that the present inventionis especially adapted. Sheet, as used in the present description,includes also .plate as known in theitrade (i.e., over A thick).However, it is understood that the principles and structures of theinvention as :herein described are not limited to the conveying ofaluminum sheets through a furnace. The invention can be equally wellemployed to convey other materials of other shapes from one locationto:another.

Each of the brush rollersvll, 12, 13 is similarly constructed and hasdisposedlabout theperiphery thereof two (helical brushes 14 and .15.Brush 14 on each roller takes the form .ofa right-hand ahelix .whilebrush 15 is a left-hand helix. The sheets are conveyed in the directionof arrow 16 and ride on top of the helical brush rollers. Reference willnow be made to Fig. 3 in describing the structural details of the brushassembly. A U-shaped channel 17 is provided and has a rod 18 passinglengthwise therethrough. The brush bristles 19 pass aroundthe rod andextend outwardly on both sides thererof as shown in cross-section inFig. 3. With the bristles 19 and rod 18 in place within the channel, thelatter is clamped or squeezed together in such a manner that small tabs21 are punched out of the channel sides at close equally spacedintervals therealong. These tabs 21 serve to firmly grip the bristlesand hold them in place.

The size of brush bristle used may vary widely, and will depend in parton the weight of the sheet being conveyed and the total number ofbristles per unit area. Additionally, the surface area of all thebristles should be sufliciently great to support the conveyed sheetwithout marking the conveyed sheet solely as a result of the weight onthe bristle tips. In one practical embodiment of the invention it wasfound that brushes of stainless steel bristles inch in length and of agauge between .004 and .006 gave highly successful results.

The brush structure of Fig. 3 is formed into a helix and may be securedto the rollers 11, 12 and 13 in any suitable manner. Any conventionalmechanism may be used to drive the rollers and as shown in Fig. 1, achain drive is employed. Each roller is mounted on a shaft 23 whichcarries a sprocket on each end thereof. A motor 24 drives brush roller11 by means of a chain 25. R- tary motion is transmitted to the rollers12 and 13 through chains 26 and 27 respectively. Alternatively, a beltand pulley driving arrangement could be employed.

It is understood from the above that as the brush rollers turn in acounterclockwise direction as viewed in Fig. 1, the aluminum sheets willpass over the tops of the rollers in the direction of arrow 16. Thepurpose of the two oppositely wound helices on each roller is tomaintain the sheet material in a straight line path. It may be readilyseen that a single helical conveying arrangement will exert a force onthe material that has a lateral or sidewise component. If this lateralforce is not compensated for, the material may move off the side of theconveyor. Thus, there is provided the double helix oppositely wound asabove described. Each helix will exert a lateral force on the materialin opposite directions which will balance. The only effective propellingforce is in the straight line direction of arrow 16.

An alternative arrangement of brushes is shown in Fig. 2. Here, aplurality of axles 28, 29 and 31 are arranged in generally parallelrelationship and mounted on suitable supporting structure (not shown).Each axle carries a plurality of brushes 32 which are secured by a huband set screw 33. Though each axle has been shown as being equipped withthree disk-shaped brushes, any convenient number may be so used. Thebrushes may be constructed as shown in Fig. 3 and can be convenientlyplaced around a center hub. The axles are driven by a motor 24A, chain25A and chain 26A similarly to the drive mechanism shown in Fig. 1. Theaxles 28, 29, 31 and disk brushes 32 rotate in a counterclockwisedirection and the aluminum sheet 34 feeds in the direction of the arrow.

Fig. 4 shows a still further embodiment of the present invention inwhich a series of straight brushes serve to support and feed theindividual sheets. In this form, a pair of shafts 35, 36 are rotatablymounted in the supporting structure, not shown) and carry a pair offriction rollers 37, 38 respectively. An endless belt 39 passes over therollers and serves to support the series of lateral brush supports 41.These supports may be equally spaced longitudinally of the belt andsecured thereto by any convenient means such as screws passing upthrough the underside of the belt and into the supports 41. The

upper edge of each support carries a straight brush 42 which may be ofthe general construction shown in Fig. 3. The system may be driven by amotor 24B through a chain 43 which encircles a drive sprocket 44 on themotor shaft and a driven sprocket 45 on roller shaft 35.

Yet another method of embodying the present inven tion would be to use aflat surface (i.e., pallet) with a surface of bristles as one type ofconveying surface.

In each of the embodiments thus far described, it was contemplated thatthe supporting or material engaging elements comprised wire brushes.However, the fundamental principles of this invention are not solimited. The objects of the invention may be realized by otherstructures, one of which is shown for example in Fig. 5. In thismodification, a plurality of rotatably mounted shafts 46, 47 support aseries of flexibly mounted fingers 48. The rollers carry a number ofrigid stubs 49 to which are secured flexible mountings 51. Thesemountings may take the form of short lengths of Wire or other flexiblematerial and serve to maintain the individual fingers in a radialposition while permitting deflection thereof by the aluminum sheet 50.

Reference will now be made to Figs. 6 and 7 in considering the manner inwhich the present invention compensates for expansion of the aluminumsheet and avoids scratching or marking thereof. The solid line element52 indicates the position of the flexible supporting element beforeexpansion of sheet 53 occurs. Element 52 may be either a wire bristle asin Figs. 1, 2 and 4 or it may be a flexible finger as in Fig. 5. Forconvenience of description, it will be referred to as a bristle. Thesolid line position of the bristle S2, is the initial relative positionit takes in contacting the sheet 53. That is, brush 52 initiallycontacts sheet 53 at contact point 54. Under the influence of thefurnace heat, the sheet may expand longitudinally thereof with thecontact point 54 shifting to point 54A. As this point shifts in relativeposition, the top or contacting point of brush 52 will similarly shiftdue to the flexible character of the wire bristles. It is seen thereforethat there is no rubbing or scraping between the sheet and bristle top.The point of contact remains constant. Consider now the lateralexpansion of sheet 53 as illustrated in Fig. 7. The brush bristle 52initially contacts the sheet at a point shown by the solid line positionof the bristle. As the sheet expands laterally, the point of contactmoves outwardly to the side but there is no relative movement betweenthe upper contacting point of the bristles and the sheet since theflexible character of the bristle permits a shifting of the end thereofto the dotted line position.

Shrinkage of the sheet 53 is compensated for in the same manner asexpansion thereof. In Figs. 8 and 9, the solid line position of bristle52 represents the position thereof before the expansion. The dottedlines represent the bristle position after expansion. The change ofposition is of course due to the movement of the contact point. However,the contact point itself does not change because the bristle follows themovement thereof as in the case of sheet expansion.

It is seen therefore that by providing a flexible supporting means forthe material, small relative movements of the sheets will beaccommodated for by the bending of the support means. Thus the originalpoint of contact remains the same and scratching or abrading of thesheet material is eliminated.

Though the present invention has been disclosed with respect to specificembodiments thereof, it is understood that these are not to beconsidered as limiting the scope of the invention as defined in theappended claim.

What is claimed is:

In combination with a heat treating chamber for metallic workpieces,conveyor means within said chamber for supporting andadvancingworkpieces through said chamber during heat treatment thereof, saidconveyor means including supporting means and flexible bristlelike ele-2,883,172 5 ments projecting from said supporting means with the freemarring of the softened supported surfaces: of said workends thereofengageable with the under surfaces of the pieces is avoided. workpiecesfor supporting the workpieces while being conveyed through said chamber;said flexible elements being References Cited in the file of this patentformed of a metal that is resistant to the heat to which 5 the metallicworkpieces are subjected and said elements UNITED STATES PATENTS beingbendable to permit their free ends to follow their 1,248,992 Barnett etal Dec. 4, 1917 points of contact with the surfaces of the metallicwork- 1,669,902 Kathner May 15, 1928 pieces during relative movement inany direction between 1,906,049 DeBack Apr. 25, 1933 said points ofcontact and said supporting means, whereby 10 2,755,086 Lubersky July17, 1956

